Manual Steering Replacement '75 Duster

I have a '75 Slant 6 Duster Base and it's my daily, and only car. The manual box needs either a serious rebuild or replacement. I need this car back on the road ASAP and would like to stay under around $600 if possible.

What I need to know is what's my best method of fixing the problem, replace or rebuild?

Should I upgrade to a quicker 20:1 or 16:1 while I'm at it?

Should I replace the pitman arm while I'm at it?

I just want as little steering play as possible and to get the car back on the road quick.

thanks for your help

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